On Fri, Aug 15, 2014 at 10:57:14AM +0900, Namhyung Kim wrote:
> Hi Jiri,
>
> 2014-08-14 (목), 16:10 +0200, Jiri Olsa:
> > On Thu, Aug 14, 2014 at 03:01:40PM +0900, Namhyung Kim wrote:
> >
> > SNIP
> >
> > > However, with --children feature added, it now can show all callees of
> > > the entry. For example, "start_kernel" entry now can display it calls
> > > rest_init and in turn cpu_idle and then cpuidle_idle_call (95.72%).
> > >
> > > 6.14% 0.00% swapper [kernel.kallsyms] [k]
> > > start_kernel
> > > |
> > > --- start_kernel
> > > rest_init
> > > cpu_idle
> > > |
> > > |--97.52%-- cpuidle_idle_call
> > > | cpuidle_enter_tk
> > > | |
> > > | |--99.91%-- cpuidle_wrap_enter
> > > | | cpuidle_enter
> > > | | intel_idle
> > > | --0.09%-- [...]
> > > --2.48%-- [...]
> > >
> > > Note that start_kernel has no self overhead - meaning that it never
> > > get sampled by itself but constructs such a nice callgraph. But,
> > > sadly, if an entry has self overhead, callchain will get confused with
> > > generated callchain (like above) and self callchains (which reversed
> > > order) like the eariler example.
> > >
> > > To be consistent with other entries, I'd like to make it just to show
> > > a single entry - itself - like below since it doesn't have callees
> > > (children) at all. But still use the whole callchain to construct
> > > children entries (like the start_kernel) as usual.
> > >
> > > 40.53% 40.53% swapper [kernel.kallsyms] [k] intel_idle
> > > |
> > > --- intel_idle
> >
> > I understand the consistency point, but I think we'd loose
> > usefull info by cutting this off
> >
> > I guess I can run 'report -g callee' to find out who called intel_idle
> > instead.. but I would not need to if the callchain stays here
>
> Yeah, but current behavior intermixes caller-callchains and
> callee-callchains together so adds confusion to users. This is a
> problem IMHO.
hum, where is it callee/caller mixed? with following example:
---
void c(void)
{
}
void b(void)
{
c();
}
void a(void)
{
b();
}
int main(void)
{
while(1) {
a();
b();
c();
}
}
---
for 'c' the current code will display:
- 43.74% 43.74% t t [.] c
▒
- __libc_start_main
▒
- 86.33% main
▒
67.08% c
▒
- 32.91% a
▒
99.44% c
▒
- 0.56% b
▒
c
▒
13.67% c
▒
and with this patch:
- 43.74% 43.74% t t [.] c
▒
c
▒
The 'c' callchain is still in caller order. IMO we should
keep whole callchain here.
jirka
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
